70 ELOPIFORM FISHES 



(Greenwood 1970a) ; the only variation is the occasional double nature of the second 

 preural vertebra. 



One of the characteristic, albeit retentional, features of the Megalopidae is the 

 presence of fringing fulcra on the dorsal surface of the upper principal caudal fin-ray. 

 Regan (1910) noted these in both Megalops and Tarpon. In both genera fringing 

 fulcra are a very late development ; in Tarpon fringing fulcra are not apparent before 

 the fish has reached 170 mm S.L. whereas in Megalops (which is a much smaller 

 species) fringing fulcra do not appear before 116 mm S.L. Tarpon never shows more 

 than four fulcra (Regan 1910) and generally only one such element is present. 

 Megalops, on the other hand, shows a prolific development of about eight in the largest 

 individuals. The fringing fulcra of Tarpon are long and slender, the anterior fulcrum 

 (generally the only one) being overlapped to a considerable extent by the posterior 

 dorsal accessory ray. Those of Megalops are short, relatively broad and are but little 

 overlapped by the preceding ray so that in many specimens examined the fulcra 

 are not easily distinguished from the terminal segments of the accessory ray. The 

 fringing fulcra are discussed further elsewhere (p. 199). 



Genus PROTARPON gen. nov. 



Diagnosis. Megalopid fishes in which the neurocranial roof is flat, marked by 

 prominent ridges. Parietals slightly longer than broad. Dilatator fossa narrow, 

 deep and roofed by pterotic and autosphenotic. Posterior opening of the jugular 

 canal below the level of the subtemporal fossa. Maximum depth of the neuro- 

 cranium at the occiput. Maxilla extending behind the eye. Operculum without 

 antero-dorsal indentation. Dentary shallow anteriorly. 



Type-species. Megalops prisons Woodward, 1901. 



Protarpon priscus (Woodward) 

 (Text-figs. 35-38) 



1844 Hypsodon toliapicus Agassiz : 5, pt. 1 : 101 (nom. nud.). 



1844 Megalops priscus Agassiz : 5, pt. 2 : 114 {nom. nud.). 



1845 Megalops priscus Agassiz ; Agassiz : 308 {nom. nud.). 

 1854 Megalops priscus Agassiz ; Owen : 172 {nom. mid.). 



1 90 1 Megalops priscus Woodward : 24, pi. 3 figs. 3-6. 

 1966 Megalops priscus Woodward ; Casier : 118. 



Diagnosis. See Woodward (1901 : 24). 



Holotype. B.M.N.H. 36070, head with opercular apparatus, the skull roof 

 crushed laterally. 



Material. The holotype and paratypes B.M.N.H. P.356, P.637, P.4i54a, 

 P. 26694 (formerly P. 1698) and P. 26743. With the exception of the holotype and 

 P. 26743 these specimens consist of the posterior half of the neurocranium in varying 

 states of preservation. The only specimens which can be definitely assigned to P. 

 priscus are those with cranial remains. 



